光子晶体结构的单曝光制造

Transparent electrodes (TEs) are the essential elements of many optoelectronicdevices such as solar cells, touch screens, organic LEDs, and LCDs. Consequently demand for TEs is growing very steeply and the market value presentlystands at 8 billion USDs. The state-of-art indium tin oxide (ITO) has an excellent trade-off between optical transparency and electrical sheet resistancebut suffers from several drawbacks, mainly the increasing cost due to indiumshortage, and inadequate flexibility due to poor mechanical ductility.This thesis presents the development of a new class of TEs based on ultrathinmetal films (UTMFs). The work started from understanding the fundamentalaspects of UTMF growth and properties, and then focused on different UTMFbased geometries, composition, and combination for potential applications indifferent optoelectronic applications.Single component ultrathin Ni and Cr flms were shown to possess significantly high transparency in the ultraviolet (175-400 nm) and mid-infrared2.5-25 um) regions making them viable TE for devices such as UV photodiodes, and IR pyroelectric detectors. The natural oxidation process, which isa major concern for metal films, has been exploited to achieve stable metallicfilms by inducing a protective oxide layer.

In another proposed novel design, incorporating an ad hoc conductive gridthe sheet resistance of UTMFs can be reduced by more than two orders of magnitude with negligible loss in transparency, which in turn eliminates the inversetrade-off relationship between optical transparency and electrical conductivityof continuous metal based TEs A TE structure based on the ultrathin conductive Cu films with an application specific functionalized capping layer of Ti or Ni layer has been demonstrated. The properties of the TE can be tuned accordingly and show excellent stability against temperature, and oxidation. The suitability of Ag-Cu alloyfilms as TE as an alternative to ITO has been also investigated. The opticalspectrum of such alloy films follows the average optical behavior of single com-ponent Cu and Ag layers, thus resulting in a much flatter optical response inthe visible region.

UTMFs combined with Al doped ZnO (AZO), which is possible ITO replace-ment, has also been demonstrated to show the possibility of hybridizing thetwo technologies. A bilayer Ag/AZO has been developed which can overcomethe high reflection of metals and retain their good electrical behavior, whilemaintaining a minimum total film thickness. In another structure, UTMFcapping layer were used to improve the stability of AZO. It was found thatan ultrathin oxidized Ni capping layer with a thickness at percolation threshold greatly enhances the stability of AZO layer in harsh environment withoutaffecting the electro-optical properties.